Research to date suggests that encouraging increased physical activity and exercise engagement may be an effective way to improve symptoms, fitness, quality of life, and reduce time spent in hospital for bronchiectasis sufferers. However, relatively few patients continue to engage with exercise programs that are of benefit to their health and symptoms. Barriers to exercise are thought to include time constraints and the use of specialist equipment (e.g. cycle ergometers) which may not be available or accessible in the home (or hospital) setting. With these points in mind, there is growing interest in brief, relatively intense, interval exercise interventions for chronic lung disease sufferers as they require minimal equipment and may more easily translate back into the home setting. Of the types of approach this might include, both stair-based and walk-based interval exercise appear to be relatively safe, practical, and time-efficient ways to improve physical fitness and quality of life in previously untrained and clinical populations. However, the feasibility and effectiveness of their use by chronic lung disease patients, particularly those with bronchiectasis, is yet to be properly examined. The investigators therefore intend to recruit 10 bronchiectasis patients to explore the feasibility and effectiveness of minimal-equipment interval exercise interventions in this population. More specifically, the investigators would like to observe patients' acute physical and perceptual responses to four different step and walk-based protocols which have been established for other clinical populations. The investigators also wish to explore whether these protocols are engaged with, and enjoyed, during a six week unsupervised exercise intervention (in the home), as well as the effects of this six week unsupervised exercise period on physical fitness. This project will hopefully make a valuable contribution to the limited research to have examined the real-world application and impact of interval-type exercise interventions on exercise behaviour, health, and symptoms in bronchiectasis sufferers.

Baseline testing (Visit 1) Having completed informed consent and screening, participants will be invited to complete a hospital-based baseline physiological testing session. The usual care of this participant group means that a clinical assessment of condition severity and associated spirometry measures (e.g. peak flow, forced vital capacity) will have already been completed which will be included in the study data. If this is not the case, then a member of the patient's usual care team (which may include members of the research team) will collect these baseline measures. Baseline physiological assessment will then be completed, including a self-paced six minute walk test (6MWT); an Isometric Quadriceps Strength Test (IQST); and an incremental, externally paced, symptom-limited Chester Step Test (CST ). Peak values for cardiorespiratory measures (i.e. heart rate, oxygen consumption and saturation, minute ventilation) will be established by way of clinically validated metabolic cart, oximeter and facemask applied during the incremental CST. Each of these tests will be delivered in the stated order across a 60 minute period, with each test followed by at least 5 minutes of rest to allow for adequate recovery and instruction.

Acute high-intensity interval exercise trials (Visits 2-5) Four subsequent hospital-based (supervised) trials will require participants to complete differing formats of step-based or walking-based HIIE, in a randomised order established by an online random sequence generator. Mean and peak values for cardiorespiratory responses (i.e. heart rate, oxygen consumption, minute ventilation) will be established by way of clinically validated metabolic cart and face-mask applied for the duration of each protocol. Whilst the same format of each HIIE session will prescribed to each participant, their completion of each work and rest period (and the duration of these) will be subject to symptom limitation (i.e. they will be permitted to shorten work and/or extend rest periods if symptoms dictate).

Post-HIIE questions will be verbally asked of participants at the end of each exercise session, including;

Did they enjoy this type of exercise? Would they like to try this exercise at home? Did they feel safe when completing this exercise? What will be the major barrier for them to not try this exercise at home?

In addition to their initial responses, participants will be invited to offer a brief explanation as appropriate. All responses will be recorded by dictaphone and subsequently transcribed by a member of the research team for later analysis.

Unsupervised 6 week high-intensity interval exercise intervention Having completed all acute high-intensity interval exercise trials, participants will then complete 6 weeks of home-based unsupervised exercise, initially incorporating their preferred format of stair and/or walking-based HIIE, three days per week. They will be encouraged to gradually progress exercise load (i.e. repetitions, work-to-rest ratio, and/or sessions per week) to a maximum of 6 x 60 seconds, five times per week (i.e. ~12 minutes total). Measures of physiological status, symptoms and well-being will be logged throughout (i.e. heart rate, dyspnea, respiratory quality of life, anxiety and depression).

Follow-up testing (Visit 6) Upon completion of home-based unsupervised exercise intervention, baseline physiological assessments will be repeated in the hospital setting. This will again include a self-paced MWT; an IQS test; and an incremental, externally paced, symptom-limited CST. Peak values for cardiorespiratory measures (i.e. heart rate, oxygen consumption, minute ventilation) will be established by way of clinically validated metabolic cart and facemask applied during the incremental CST. Each of these tests will be delivered in the stated order across a 60 minute period, with each test followed by at least 15 minutes of rest to allow for adequate recovery and instruction.

Following a similar approach to pre-intervention testing, post-intervention questions will be verbally asked of participants at the end of the follow up testing session, including; Did they enjoy this exercise intervention? Would they like to continue these types of exercise at home? Did they feel safe when completing these exercises at home? What will be the major barrier for them to not continue these types of exercise at home? What changes would make continuing this type of exercise more appealing to them?

In addition to their initial responses, participants will be invited to offer a brief explanation as appropriate. All responses will be recorded by dictaphone and subsequently transcribed by a member of the research team for later analysis.

Inclusion Criteria:

• Male or female adults (i.e. >18 years)
• Clinical diagnosis of non-cystic fibrosis bronchiectasis.
• Registered/treated as an inpatient or outpatient with the United Lincolnshire NHS Trust
• Capable of giving informed consent.
• Deemed eligible for pulmonary rehabilitation (including exercise) by clinical specialist, specialist nurse, or respiratory physiotherapist.
• Has not met national guidelines for exercise engagement during the preceding 3 months (i.e. completing at least 150 minutes of moderate aerobic activity or 75 minutes of vigorous aerobic activity each week).

Exclusion Criteria:

• Inability or unwillingness to sign informed consent;
• Outside of stated age range (i.e. <18 years);
• Pregnant;
• Suffering from any major co-morbidity known to impair exercise tolerance (i.e. heart failure/disease, diabetes, neuromuscular and/or musculoskeletal disease or injury) or another factor considered as a contraindication to clinical exercise testing by clinical specialist respiratory physiotherapist;
• Has met national guidelines for exercise engagement during the previous 3 months (i.e. completing at least 150 minutes of moderate aerobic activity or 75 minutes of vigorous aerobic activity each week)